Geological structure of the Pre-jurassic basement of the Yugansk-Koltogorsk zone of the West Siberia

Abstract

Subject of the study. We have carried out an additional exploration on petrography, petrochemistry, geochemistry, geochronology and biostratigraphy of rock complexes of the Yugansk-Koltogorsk (central part of West Siberia). Materials and methods. The materials are core samples from wells that penetrated the Pre-Jurassic basement rock complexes The used methods are as follows: X-ray spectrum microanalysis (Cameca SX 100, JEOL-733 Superprobe); the silicate analysis of the rocks (СРМ-18 and EDX-100); mass-spectroscopy with inductively coupled plasma (ICP-MS) (ELAN-9000 and Element2); zircons were analysed with a high resolution ionic microprobe SHRIMP-II (U-Pb); Ar-Ar dating was carried out by Micromass 5400; biostratigraphy, petrochemestry. Results. A geological map of Yugan-Koltogor zone of the central part of West-Siberian plate in a scale 1:500 000 was created. The map is a set of informational geological, geophysical and other layers. It was established that age of granites is Early Permian, the basalts of the rift zone began to form 268.4 ± 7.5 Ma ago (Ar-Ar). Conclusions. Volcanism in the axial rift zones of the West-Siberian megabasin basement began earlier than it is supposed before our study and significantly earlier of that of trap basalts of Siberian platform.

Keywords

• west-siberian basin
• pre-jurassic basement
• tectonics
• oil and gas bearing
• u-pb
• ar-ar age
• geochemistry
• permian-triasic basalts
• mineralogy